Extracorporeal ultrasonic medical device

ABSTRACT

Ultrasonic devices for preventing microbubbles and/or microparticles from reaching the brain during a PCI or cardiovascular surgery. Devices  27  and  77  are designed for implantation in the chest cavity and operate in combination with needle vents or other vent systems for removing diverted microbubbles. Systems  77  and  83  are designed for noninvasive employment. Devices  57  and  87  are particularly designed to prevent microbubbles from reaching the great origins of the carotid arteries and/or for diverting bubbles that might reach the vicinity and otherwise pass through. Improved devices  11  and  94  separate microbubbles from a flowing bloodstream and produce a cleansed stream.

This application is a Divisional of U.S. application Ser. No.12/345,486, filed Dec. 29, 2008, which is a divisional of U.S.application Ser. No. 11/245,583 filed Oct. 7, 2005, which is aDivisional of U.S. application Ser. No. 10/162,824 filed Jun. 4, 2002,which is a continuation of PCT/IB00/01785, filed Dec. 4, 2000, whichapplication claims priority from U.S. Provisional Application Ser. No.60/190,839, filed Mar. 20, 2000, and U.S. Provisional Application Ser.No. 60/169,226, filed Dec. 6, 1999, the disclosures of which areexpressly incorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The invention relates generally to devices which employ ultrasonic wavesfor removal of contaminants from liquids, and more particularly theinvention provides devices and methods for medical treatment that employthe imposition of ultrasonic energy to a flowing stream of blood so asto deflect and/or remove small bubbles and/or particles that may beentrained therein.

BACKGROUND OF THE INVENTION

Sound waves may be viewed as being generally mechanical from thestandpoint that they consist of the vibration of molecules about theirequilibrium positions, and they are accordingly best transmitted throughsolid media. Sound waves with frequencies above the upper limit audibleto the human ear (about 18,000 Hz) lie in the ultrasonic range. Thereare two main classes of ultrasound presently in clinical use: (1) Highfrequency (5-7 MHZ), low-power ultrasound, which is employed extensivelyin diagnostic ultrasonography; and (2) Low-frequency (20 to 45 kHz),high power ultrasound which has recently been put to therapeutic use.

It has been known for some time that the application of acoustic energyor force for a stream of flowing liquid, such as blood, will have aneffect upon the behavior of gas bubbles entrained therein. An articleentitled “Acoustic Effects on Gas Bubbles In the Flows of Viscous Fluidsand Whole Blood” appeared in the Journal of Acoustical Society ofAmerica, 53, 5, 1327-1335, I. C. Maceto and Wen-Jeo Yang (1973), whichdiscussed the use of acoustic or ultrasonic waves to trap small bubblesagainst the wall of the tube in which the liquid stream is flowing,using liquids that resemble whole blood in their rheological property;it was shown that the bubbles could be deflected and trapped against thesidewall of the tube in which flow is occurring. In 1992, Schwarz, KarlQ. et al., published an article entitled “The Acoustic Filter: AnUltrasonic Blood Filter for the Heart-Lung Machine”, in the Journal ofThoracic and Cardiovascular Surgery, 104, 6, 1647-1653 (December 1992).This article indicated that microbubbles in a chamber can be pushed tothe opposite end of the chamber where they can be accumulated andeventually carried through a waste port, as a result of which it wouldbe feasible to use acoustic radiation force to filter small gas bubblesfrom blood, while cautioning that such ultrasonic energy might causeimplosion of gas bubbles that could potentially result in blood trauma,e.g. hemolysis, and thus should possibly be avoided for such reason.

U.S. Pat. No. 5,022,899, entitled Sonic Debubbler for Liquids, disclosesdevices that employ an ultrasonic transducer to produce low poweranisotropic sound waves at about the resonant frequencies of bubbles todrive the bubbles in a specific direction where they would be rejectedby being drawn out through a fluid outlet port or trapped in adisposable open cell bubble trap. Power levels are regulated so as toremain below a level which would cause hemolysis from cavitation. U.S.Pat. No. 5,334,136 shows a system for reducing post-cardiopulmonarybypass encephalopathy due to microembolization of the brain of a patientas a result of microbubbles that may arise during open-heart surgerywhen a cardiopulmonary bypass machine is employed. The patient'sbloodstream is subjected to an ultrasonic traveling wave which isdirected across the stream of blood without reflection so as to sweepthe blood clean of microbubbles without inducing blood cell trauma. Themicrobubbles are carried by the traveling wave to a waste exit port.

Although such early devices as those in the above-identified U.S.patents showed the principle to be sound, devices for more efficientoperation have continued to be sought as well as devices that could beassociated directly with the human body itself so as to have an effectupon the internal bloodstream in a patient who is undergoing treatment.

SUMMARY OF THE INVENTION

The invention provides devices for the removal of contaminants fromliquids, and more particularly devices for medical treatment of apatient undergoing cardiac surgery or a percutaneous cardiologicalintervention (PCI), which devices utilize acoustic or ultrasonic energyto cause microbubbles and/or microparticles traveling in a flowingstream of liquid, such as blood, to be deflected in a specific manner inorder to efficiently either effect their removal from the flowing streamor to block their entry to a critical portion of the human body, such asthe neck vessels leading to the brain.

In one particular aspect, the invention provides a medical treatmentdevice for removing microbubbles and/or microparticles from the blood ofa patient, which device comprises transducer means for surrounding aconduit within which a stream of liquid is flowing, a sidestream-removaltube unit for location downstream of said transducer means and axiallywithin said conduit which is operable to withdraw the central portion ofsaid flowing stream, and power means for operating said transducer meansto direct ultrasonic energy radially inward about 360° so as toconcentrate microbubbles and/or microparticles centrally in the flowingstream where they can be withdrawn through said tube unit.

In another particular aspect, the invention provides a medical treatmentdevice for removing microbubbles and/or microparticles from a patient'sbloodstream, which device comprises transducer means for associationwith the exterior surface of the posterior side of the aorta in thegeneral region of the transverse sinus, means for powering saidtransducer means to generate ultrasonic waves that are directed towardthe anterior side of the aorta, a needle vent for insertion into theanterior side of the aorta downstream of the transverse sinus, and meansfor removing blood and microbubbles and/or microparticles through theneedle vent.

In one more particular aspect, the invention provides an improved bubbletrap which is designed to physically remove air bubbles andmicroparticles from a sidestream of liquid such as that diverted in thedevice of FIGS. 1 and 2, which would be particularly useful in treatingdiverted blood from a heart-lung machine or the like.

In yet another particular aspect, the invention provides a method forgenerating ultrasonic waves either adjacent an external surface of thebody of a patient or within the esophagus or trachea of a patient anddirecting those waves toward the aorta so as to cause microbubblesand/or microparticles traveling in the patient's bloodstream in theaorta to deviate in a preselected direction from normal direction offlow.

In still another particular aspect, the invention provides a method fortreating a patient undergoing a PCI or open-heart surgery, so as toremove microbubbles and/or microparticles from the blood of the patient,which method comprises focusing ultrasonic waves into the left ventricleand/or the ascending aorta of the patient to direct microbubbles and/ormicroparticles so they will reach a region along the anterior wall ofthe ascending aorta, and withdrawing said microbubbles and/ormicroparticles from the bloodstream through vent means extending throughthe anterior wall of the aorta.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a medical treatment device embodyingvarious features of the invention shown as it might be operated with thestream of blood exiting from a heart-lung machine which would be hookedup to a patient undergoing cardiac surgery.

FIGS. 2A and 2B are perspective views of a transducer employed in FIG. 1shown in the closed and open positions.

FIG. 3 is a sagittal, longitudinal sectional view showing the aorticroot, a needle vent to which suction is applied, and an acoustic devicewhich includes multiple piezoelectric crystals (shown in cross-section),with the plane along which the view is taken passing vertically throughthe transverse sinus.

FIG. 4 is a view taken along line 4-4 of FIG. 3, showing the root of theaorta with the device situated in the transverse sinus, stabilized witha spring on the patient's right side of the aorta and with tensioncreated by inflation of a rubber balloon located on the patient's leftside.

FIG. 5 is a view of an alternative medical treatment device generallysimilar to that shown in FIGS. 3 and 4 which employs a double lumencannula.

FIG. 6 is a perspective view showing an arterial-line double lumencannula.

FIG. 7 is a view showing another embodiment of a medical treatmentdevice embodying various features of the invention which is designed tobe associated about the neck of a patient undergoing cardiac surgery ora PCI.

FIG. 8 is a schematic view of a pad embodying various features of theinvention and containing multiple transducers that might be used in thechest of a patient positioned underneath the heart as a part of a methodof medical treatment, e.g. during open heart surgery.

FIG. 9 is a view illustrating medical treatment wherein a modifiedesophageal probe is positioned in the esophagus so as to directmicrobubbles and/or microparticles in the aorta anteriorly to awithdrawal vent, e.g. the smaller lumen of a double-lumen cannula suchas that shown in FIG. 6.

FIG. 10 is a view similar to FIG. 8 showing an alternative embodiment ofthe transducer-carrying pad that might be exteriorly placed against theback of a patient.

FIG. 11 is a perspective view of an endotracheal tube useful in onemethod of the invention which is shown with a positioning ballooninflated.

FIG. 11A is a cross-sectional view enlarged in size, taken along theline A-A of FIG. 11 showing the tube positioned in a patient's trachea.

FIG. 12 is a front view of the ascending aorta, the trachea and theesophagus which shows the bifurcation of the trachea and the closerelationship between the trachea and the aortic arch between theascending aorta and the descending aorta.

FIG. 13 is a schematic view which shows an improved ultrasonic debubbleruseful for treating a diverted stream of liquid containing air bubblesand/or microparticles and producing a cleansed stream with all suchcontaminants removed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Inasmuch as air bubbles found in the bloodstream will often originate ina heart-lung machine, manufacturers of such machines have provided veryfine blood filters located between the heart-lung machine and thepatient. Unfortunately, despite such precautions, there are substantialindications that so-called “arterial-line” microbubbles still reach thepatient, and once they reach the patient, they very likely will reachthe brain where they will frequently result in neurological damage. Ithas now been found that a more efficient bubble-removal device can beconstructed which utilizes the known principles of the prior artdevices.

Illustrated in FIG. 1 is an improved removal device for withdrawing airbubbles or microparticles that might be entrained in a flowing stream ofliquid, such as blood which is being discharged from a heart-lungmachine or some similar device. The removal device 11 includes a tubularbody 13 which is formed with threaded connectors 15 a and 15 brespectively at the inlet and outlet ends. The body is circular incross-section and has an enlarged region 17 near the inlet end, ofgreater diameter than either the inlet or the outlet, which graduallysmoothly reduces to an outlet having about half of the enlargeddiameter. A vent tube 19 is located just upstream of the outlet in aregion where the tube 13 has narrowed to a continuous diameter section.The vent tube is fixed to the wall of the tubular body 13 and has anentrance section 19 a that is coaxial therewith and an oblique sidesection 19 b through which a small stream of liquid is removed from themain stream flowing through the device 11.

Surrounding the enlarged diameter region 17 is a transducer 21 ofannular shape. As depicted in FIGS. 2A and 2B, the annular transducer 21is preferably made in two halves that are interconnected by a hinge 23so that the transducer might be placed around an existing conduit ifdesired. The space between the transducer 21 and the tubular body 13 isfilled with water or with a jelly substance so that there will be a goodflow path for acoustic energy therethrough.

When for example blood being discharged from a heart-lung machine isbeing returned to the body of the patient, it may include small bubblesof air and/or microparticles, which it is important be removed prior toreturn to the body of the patient. By discharging the stream into anenlarging region, there is more time for particles and/or bubbles to beacted upon by acoustic energy at this point. The annular transducer 21is operated so as to generate ultrasonic waves and direct them radiallyinward towards the center for 360° about the circumference of the tube.Accordingly, microbubbles and/or microparticles will be uniformlyconcentrated in the very center of the flowing stream and willaccordingly be removed through the downstream vent tube 19 through whichthere is continuous withdrawal of a sidestream using a roller orsinusoidal pump, or any other suitable type of pump that will direct thesidestream to a filter to remove microparticles and small bubbles, suchas that described hereinafter with respect to FIG. 13. If the liquidbeing treated is blood, one would then recirculate the blood to theheart-lung machine or return it for another pass through the removaldevice.

Illustrated in FIGS. 3 and 4 is a removal system 27 which is designedfor association with the ascending aorta at a location just downstreamfrom the aortic valve. The device 27 is designed for placement in thetransverse sinus and is operated so that air bubbles and/ormicroparticles during all levels of the flow of blood from the leftventricle of the heart are directed toward the anterior aspect of theascending aorta. A transducer in the form of multiple piezo crystals 29arranged as an annular array is located exterior of the aorta with thecrystals being are aimed in different directions generally across theblood flow. Flow rate is monitored and flow rate-dependent, sequentialpulses are used to cause the air bubbles to translate in an anteriordirection as well as to cause them to cavitate and coalesce with othersmall bubbles to create larger ones. A needle vent 31 is insertedthrough the anterior wall of the aorta, and suction is continuouslyapplied during active operation.

Suitable signals to cause generation of high frequency and/or lowfrequency ultrasound waves may be transmitted simultaneously byactivating a pulse generator connected to the various piezo crystals.The employment of a multitude of crystals is preferred so that some maybe dedicated to providing high frequency sound waves; however, it mayalso be satisfactory to use the same crystals to alternately produceultrasound of the two different desired frequencies. Low, high and mixedfrequency sound waves are generated as long as the system continues todetect bubbles passing through the needle vent. Only when no furtherbubbles are being detected, as by a Doppler sensor, is the needle ventoperation discontinued and the vent removed. The system can thereafterbe switched into another mode so that it operates as a Doppler-typeflow-measuring device. In this mode, the system is able to provide thesurgeon with important information to allow a studied decision to bemade as to when the patient may be taken off the bypass machine, e.g. byproviding indexes such as Cardiac output in liters/min or inliters/min/Kg body weight.

As shown schematically in FIG. 4, which is a cross-section through theaorta looking downstream, the device may include a spring-like holder 33that extends for about 210° of the circumference of the aorta andpositions the piezo crystals 29 at the desired posterior location. Thus,the holder 33 will generally be associated with the patient's right sideof the aorta, and tension in the spring-like device is created simply bythe inflation of a rubber balloon 35 located on the patient's left sideas at the location of the transverse sinus with the balloon being simplyinflatable through a simple syringe 37 or other device for feeding airinto the balloon. To monitor the bubbles that are being removed throughthe needle vent, a Doppler sensor 39, as well known in the art, may beemployed which would feed information to a central control box 41. Thecontrol box 41 could be placed next to other monitoring devices usedduring cardiac surgery and controlled by an anesthesiologist. It wouldnormally include the pulse generator for feeding energy to the piezocrystals 29 in an impulse-flow synchronizing system. If desired, asuitable mechanism may also be included to monitor cardiac outputmeasurements to assist the surgeon in deciding when the patient shouldbe removed from the cardiopulmonary machine. In addition to a read-outfrom the Doppler sensor 39, the control box might also have acoustic andvisual signal displays. Suitable cables leading from the control box 41would connect to the transducer piezo crystals 29 and to the Dopplersensor. As with all medical devices of this type, the portions thatshould be implanted within the body may be of disposal design or theycould be made permanent by employing materials that can be sterilizedafter use.

Shown in FIGS. 5 and 6 is an alternative device wherein a similartransducer system to that depicted in FIGS. 3 and 4 is employed. Anarray of piezoelectric crystals 29 is located along the posteriorsurface of the aorta just downstream of the aortic valve, and although aneedle vent 45 is shown, it is optional because, just downstream thereofin the anterior wall of the aorta, there is inserted a double-lumenarterial-line cannula 47.

When a patient is connected to a heart-lung machine, the venous blood isdrained from the right atrium and transmitted to the heart-lung machinefor oxygenation before being returned to the patient's arterial system.A return connection is generally established through the installation ofan aortic cannula which penetrates the aorta via a stab-wound insertioninto the anterior aspect of the ascending aorta. A needle vent 45similar to that depicted in FIG. 5 may be employed at about this samegeneral location just upstream of the aortic cannula to remove airbubbles in the oxygenated bloodstream flowing downstream from the aorticvalve that would otherwise enter the arterial system of the patient. Theoperation of such a needle vent 45 is of course greatly enhanced by theultrasonic wave-generating device, as described with respect to FIGS. 3and 4.

Using the double-lumen cannula 41 illustrated in FIGS. 5 and 6, a singlepenetration of the aorta can be used both to return the oxygenated bloodto the circulatory system and to take the place of the needle vent shownin FIG. 3. However, it can also be used in combination with a needlevent, as illustrated in FIG. 5, to supplement operation during the majorportion of the cardiac surgery. Sometimes not all of the blood will bedrained from the right atrium into the heart-lung machine, and such willbe oxygenated in the lungs if the patient is being ventilated. As aresult, this blood will reach the left atrium and thereafter will flowthrough the left ventricle. Moreover, during the performance of theproximal anasthomoses in coronary artery bypass surgery, for example,constant suction is applied to the needle vent, thus causing some air toenter into the coronary arteries, the aorta and the left ventriclebecause the aorta is under negative pressure.

The returning blood flows through a large diameter cannula 49 of thedevice into the ascending aorta, while a second smaller diameter cannulaor tube 51, which is integrally attached to the exterior of the largediameter cannula, is used to carry out a function similar to that of theneedle vent 33 in FIG. 3. The small cannula 51, which alternativelycould be located interior of the large cannula with an appropriateopening in the sidewall, has an opening 53 that faces in exactly theopposite direction from that of the lumen of the large cannula fromwhich the oxygenated blood is being discharged. Accordingly, the returnstream of oxygenated blood is discharged so as to flow downstreamthrough the ascending aorta, whereas the smaller diameter lumen isstrategically located so as to remove a small stream of potentiallybubble-containing blood that has passed through the aortic valve, i.e.in order to prevent potential bubbles in the blood from reaching thebrain and other susceptible organs. The preferable inclusion oftransducers 29 exterior of the aorta, as optionally depicted in FIG. 5,directs any bubbles toward the needle vent and/or the small diameterlumen as explained hereinbefore. Such a small side stream of blood beingremoved through the smaller lumen 51, and optionally also through aneedle vent 45, is achieved through the use of a suction pump or thelike, as explained with respect to the FIG. 3 embodiment, and all thisblood is returned to the reservoir of the heart-lung machine during thisportion of the operation.

When used with the exclusion of any needle vent, the double-lumencannular 47 avoids the necessity of having to make a second puncture inthe aorta; however, even when used in combination with a needle vent 45,the device allows venting to continue after the time that a needle vent45 is usually removed to allow the construction of the proximalanasthomoses on a beating heart, as is commonly done in coronary arteryby-pass surgery. In by-pass surgery, it is common to connect the veingrafts to the ascending aorta at about the location where the needlevent 45 is located in FIG. 5. Accordingly, when the connections to theaorta are ready to be made, the needle vent must be removed, and at thistime, the heart will begin beating so there will be some blood flowingout of the left ventricle through the aorta. Moreover, this period oftime may be as long as about 45 minutes, i.e. from the time that theneedle vent would be removed until the patient is taken off of theheart-lung machine. It can thus be realized that the ability to continueto remove a small stream of potentially bubble-containing blood throughthe novel double-lumen cannula can be particularly advantageous to thepatient.

Depicted in FIG. 7 is a collar 57 that is sized to be placed around theneck of a patient who is undergoing a PCI, such as an angioplasty or anangiography, by-pass surgery, valve repair or replacement or othercardiac surgery. The collar 57 may encircle the patient's neck for 360°,or it may be a U-shaped piece of flexible material having a pair of armsthat carry the transducers. At selected sites in the interior surface ofthe collar 57, single or multiple transducers 59, e.g. piezoelectricelements, are embedded. These may be placed on only one side of theneck, but they are preferably placed on both sides as shown in the FIG.7 embodiment. The transducers 59 are connected by electric cables to apulse generator in a control box (not shown) such as that in FIG. 4. Thetransducers 59 are oriented so as to be aimed at both great origins 61of the neck vessels, where the carotic arteries leave the aorta 62 alongthe arch 63 of the aorta and travel upward to the brain. When a patientis placed on the heart-lung machine, ultrasonic waves are generated bythe transducers 59 and sent toward the two origins 61, therebyeffectively blocking both large and/or small air bubbles andmicroparticles, such as atherosclerotic-detached debris particles fromthe patient's aortic wall as well as thrombi and calcium-cholesterolparticles, from entering into the neck vessels. These directional wavescause any bubbles to deviate from a potential path that would otherwisecarry them through a great origin 61; instead, they remain in the bloodflow in the aorta, which is flowing into the remainder of the body, e.g.to the liver, the gut, the legs, etc. As a result, potential damage tothe brain which is particularly sensitive to air in the bloodstream isavoided.

Because the collar device may need to be operated for a lengthy periodof time during a PCI or open-heart surgery, the collar 57 preferablycontains a set of transducers 59 on both sides of the neck, as shown,and the set of transducers on each side is focused upon both of thegreat origins 61. In order to avoid potential adverse side effects uponthe body itself from these ultrasonic waves, the device is operated toalternately send signals first to the set on one side for a few minutesand then to the set on the other side to generate the desired wavepatterns in the regions of the great origins 61 without substantiallyheating or otherwise affecting the patient's flesh.

Because no system of this type is perfect, it may also be desirable toinclude a second or auxiliary smart collar 71 that is focused atlocations downstream of the great origins 61, namely the location wherethe carotid arteries split prior to entering the skull. At this locationthere are two branches, an internal carotid 67 which supplies the brainand an external carotid 69 which supplies the facial structure. Thisauxiliary collar 71 will contain transducers that are focused at theregion just upstream of the junction where the split into the internaland external carotids occurs, and it will serve as a back-up that willcause any bubbles and/or solids, i.e. atherosclerotic or other debrisparticles, that may enter to the great origin to be diverted to theexternal carotid which supplies the facial structures. Thus, it providesa second level of defense to guard against such reaching the brain.

Shown in FIG. 8 is an ultrasonic device which focuses on the heartitself and particularly on the left ventricle. The device includes arelatively flat pad 73 of a size and shape to generally be insertedbelow the heart in a supine patient and through the transverse sinus sothat the heart would rest upon the pad, with the pad being positionedbelow the region of the left ventricle. The pad 73 has incorporatedtherein a plurality of transducers 75 which are operated so as to createultrasonic waves that move vertically upward through the blood in theleft ventricle and thus preferentially cause microbubbles to collect atthe highest vertical point or apex in the left ventricle of the patient,who is positioned in the supine position with his chest open. The devicecould be operated separately, or it could be operated in combinationwith a device such as that shown in FIGS. 3 and 4 which focuses uponmicrobubbles in the bloodstream that have traveled through the aorticvalve. Once the patient has been taken off the heart-lung machine, andoptionally at various times during the operation, the surgeon may removecollected air from the heart by simple insertion of a needle into theleft ventricle at its apex, withdrawing the air and a minor amount ofblood by suction.

As an alternative to placing such a transducer-carrying pad beneath theheart, one can utilize the proximity of the esophagus to the leftventricle of the heart to create a similar effect from the interior ofthe esophagus. A commercially available trans-esophageal probe can beeasily modified so as to carry a set of transducers similar to thoseshown in the collar 57 in FIG. 7. These transducers can be aligned so asto generate and direct ultrasonic waves to accomplish a pattern ofupwardly traveling ultrasonic waves roughly similar to those created bythe pad shown in FIG. 8.

Illustrated in FIG. 9 is the use of a modified esophageal probe 77 whichcontains transducers suitable for directionally transmitting ultrasonicwaves in a manner similar to the transducers 29 described previously.The esophagus is located in the body adjacent the left ventricle of theheart and the aorta. Esophageal probes that include ultrasonictransmitters and receivers are well known in the art and are describedin U.S. Patents such as U.S. Pat. Nos. 5,409,010, 5,105,819, 4,757,821and 3,951,136. Such probes of this basic nature are commerciallyavailable today throughout the world by vendors such as Deltex Medical,Medtronic Functional Diagnostics and Neomedix Systems and other vendors.Although probes of this general type have heretofore been used fordiagnostic purposes, it has now been found that by employing transducersof the type herein described suitable for creating ultrasonic acousticenergy in the ranges of interest, a modified esophageal probe can becreated incorporating such transducers and no receivers, such as areincluded in esophageal probes presently in use. Multiple transducerassemblies for creating ultrasonic waves for other purposes are shown inU.S. Pat. Nos. 6,126,619, 5,879,314 and 5,269,291. Signals would be sentto the transducers through an appropriate electrical connection 79outside of the body so as to travel along the probe to the location ofthe set of piezo crystals or the like and activate the transducers. Byproperly manipulating the esophageal probe, the surgeon will be able toalign it to focus the ultrasonic waves so as to cause the microbubblesto be directed upward to the highest point in the left ventricle wherethey would collect and also focus waves to move anteriorly in theascending aorta. Then, as previously described, either periodically, orat the end of the operation, the surgeon might manually lift the apex ofthe heart and puncture it with a suitable needle to withdraw thecollected air by suction. Moreover, by also focusing ultrasound waves atthe ascending aorta just downstream of the aortic valve, the device willalso function in a manner similar to that described with respect to thetransducers 29 in FIGS. 3 and 4 to cause gas bubbles and/ormicroparticles, such as atherosclerotic and other debris particles, tobe diverted anteriorly to a location where a needle vent and/or a doublelumen cannula would be installed in the aorta.

As an alternative to employing an esophageal probe for this function ofdiverting the gas bubbles in the heart or in the aorta as describedabove, it has also been found that such diversion can also benoninvasively achieved through the employment of a flat pad 83 that ispositioned against the back of the patient undergoing surgery.

A large pad 83 having a plurality of transducers 85 is illustrated inFIG. 10 which is designed to be positioned entirely exteriorly adjacentthe back of the patient. As shown, the pad would be adhered to thepatient's back just posterior of the heart and the aorta in a similarmanner to that in which ECG electrodes are attached. The surgeonhandling the operation would decide which of the individual transducers85 in the lattice-like array would be selectively activated so as to,for example, focus ultrasonic waves on the left atrium, the leftventricle and the ascending aorta. Thereafter, the selected transducersin the pad would be caused to operate, after the chest had been opened,to direct ultrasonic impulses for the same purpose as describedhereinbefore with regard to the esophageal probe and with respect to theinternal pad that was placed directly beneath the heart.

Instead of using a modified esophageal probe, a modified endotrachealtube 87 (illustrated in FIG. 11) may alternatively be employed inanother noninvasive method of diverting microbubbles and/ormicroparticles from entering the great origins. As illustrated in FIG.12, the ascending aorta is located adjacent the trachea (T), and theaorta arch (A) lies just above the bifurcation of the trachea.Accordingly, it can be seen that the location of a transducer at thislocation in the trachea will allow ultrasound to be directed at theaortic arch, and it can be employed in the same manner as the collar 57for diversion of contaminants away from the great origins.

Endotracheal tubes have been used for some time to carry ultrasonictransducers and receivers in order to monitor the rate of flow of bloodin the aorta, and U.S. Pat. Nos. 4,886,059 and 4,722,347 disclose suchdevices for use in monitoring blood flow.

The modified endotracheal tube 87 consists of flexible plastic tubing 89of a length sufficient to extend from outside the body to the vicinityof the bifurcation of the trachea, entering either through the nasal ororal cavity or through a surgical opening in the case of a patient whohad a tracheotomy. The illustrated device is adapted for oral insertion.Near the distal end, a transducer comprising a plurality ofpiezoelectric elements 91 is mounted on the exterior surface of thetubing 89. Electrical conductors 90 extend the length of tubing 89 forconnection of a pulse generator (not shown) to the transducers.

To positively locate the tube 87 in the trachea, T, and to provide agood path between the transducers 91 and the inner wall of the trachea,a donut-shaped cuff or balloon 93 is provided which also seals thetrachea. The endotracheal tube 87 is placed to locate transducers 91 inthe trachea, generally at a location just above the trachealbifurcation, and then rotated as needed to point them toward the aorticarch. For ventilation purposes it is necessary to seal the trachea, andthe transducers 91 should be held in position within the trachea andfocused toward the aortic arch. The donut-shaped cuff or balloon 93effectively seals the trachea and holds the tube and the transducersthat it carries in place. Inflation of the balloon 93 is accomplishedvia an inflation tube 94 using conventional fluid, preferably acousticjelly or water, that assures good acoustic transmission to the trachealwall. In other respects, the endotracheal tube 87 is constructed inaccordance with recognized ANSI standards for construction ofendotracheal tubes. In particular, the distal end suitably is providedwith a standard bevel opening and oppositely directed Murphy eye.

Multiple transducers 91 may be designed to occupy an elongated annulararray, as best seen in FIG. 11A, where they would cover an arc of about90 to 120° of the exterior of the plastic tubing 89 at a location nearthe distal end thereof within the inflatable cup, and the device wouldbe oriented by the anesthesiologist so that they would face the aorticarch. Because of the proximity between the trachea and the arch of theaorta, it can be seen that this device can be actuated and manipulatedfrom outside the body of the patient to noninvasively effectively divertpotentially harmful microbubbles and/or microparticles so they do notenter the great origins.

In various of the aforedescribed devices, a separate sidestream of bloodcarrying the microbubbles and/or microparticles is diverted from a mainbloodstream. Although various methods have long been provided forfiltering this stream to remove these contaminants, an improved andparticularly effective ultrasonic bubble trap 94 is illustrated in FIG.13 which can be used for removing bubbles and microparticles from aflowing stream of liquid. The improved trap includes a main tube 95which has a side outlet 96 that leads to a valved flask 97 or the like,entering at a location in the upper vertical half thereof. A pump P,such as a roller or sinusoidal pump, is included in the line 96 and canbe used to raise the liquid to a higher vertical level above the tube95. A normally closed valve 98 is provided at the apex of the flask, andthe body of the flask is filled with a fibrous material 99 that is inertto blood or whatever liquid is being treated. Located below and upstreamof the entrance to the side outlet is an elongated array of transducers101 operated as hereinbefore described so as to generate ultrasonicwaves that deflect microbubbles and/or microparticles upward against theupper wall of the tube 95 where they will be carried out the side outlet96 with a small stream of liquid while the remainder of the liquid flow,now cleansed of these contaminants, flows downstream to the outlet 103from which it might be sent to a reservoir, or if the liquid is blood,it would be ultimately returned to the patient. Once the liquid entersthe flask 97, any microparticles would tend to adhere to the fibrousdebubbling material 99 while air, via gravity, travels upward andcollects in the upper region of the flask from which it can beperiodically withdrawn through the valve 98. The flask may be mounted onany horizontal surface so that the liquid flows downward through thefibrous material 99 and out a lower outlet 104 driven by gravity. Theflask 97 is optionally supported upon a pad 105 which containsadditional transducers that are focused upward and actuated by a pulsegenerator (not shown). If the liquid being treated is blood, theestablishment of upwardly directed ultrasonic waves will assure theseparation of all microbubbles therefrom rather than relying upongravity alone. In the illustrated version, the cleansed sidestream isreturned to a side inlet 106 located upstream of the side outlet 96 inthe tube 95. Alternatively, the cleansed stream could be insteaddirected via an outlet tube (indicated by dot-dash outline) to aCardiotomy reservoir.

Although the invention has been described with regard to a number ofpreferred embodiments, it should be understood that various changes andmodifications as would be obvious to one having ordinary skill in thisart may be made to the invention without departing from the scopethereof which is defined in the appended claims.

1. A medical treatment device for removing microbubbles and/ormicroparticles from a patient's bloodstream, which device comprises atransducer means for association with the exterior surface of theposterior side of the aorta in the general region of the transversesinus, means for powering said transducer means to generate ultrasonicwaves that are directed toward the anterior side of the aorta,sidestream-removal means for insertion into the anterior side of theaorta downstream of the transverse sinus, and means for removing bloodand microbubbles and/or microparticles through said sidestream-removalmeans.
 2. The medical treatment device according to claim 1 whereinmeans is provided for holding said transducer means in physical contactwith the exterior surface of the aorta.
 3. The medical treatment deviceaccording to claim 2 wherein said holder means includes a spring-likesupport that fits more than 180° about the aorta.
 4. The medicaltreatment device according to claim 3 wherein expandable balloon meansis located so as to lie between said support and said transducer meansto hold said transducer means firmly against the exterior surface of theaorta.
 5. The medical treatment device according to claim 1 wherein saidsidestream-removal means is formed integrally with an arterial-linecannula for returning blood from a heart-lung machine to the aortadownstream of the aortic valve so as to constitute a double-lumencannula.
 6. The medical treatment device according to claim 5 whereinsaid double-lumen cannula has a main passageway through which incomingblood exits downstream and a smaller lumen passageway having an openingwhich faces directly upstream.
 7. The medical treatment device accordingto claim 1 wherein said transducer means includes a plurality of piezocrystals.
 8. The medical treatment device according to claim 7 whereinsaid plurality of crystals provide high frequency sound waves.
 9. Themedical treatment device according to claim 7 wherein said plurality ofcrystals provide ultrasound of low and high frequencies.